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首页> 外文期刊>Journal of Molecular Biology >Crystal structure of the extracellular domain of a bacterial ligand-gated ion channel.
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Crystal structure of the extracellular domain of a bacterial ligand-gated ion channel.

机译：细菌配体门控离子通道的胞外域的晶体结构。

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摘要

The crystal structure of the extracellular domain (ECD) of the pentameric ligand-gated ion-channel from Gloeobacter violaceus (GLIC) was solved at neutral pH at 2.3 A resolution in two crystal forms, showing a surprising hexameric quaternary structure with a 6-fold axis replacing the expected 5-fold axis. While each subunit retains the usual beta-sandwich immunoglobulin-like fold, small deviations from the whole GLIC structure indicate zones of differential flexibility. The changes in interface between two adjacent subunits in the pentamer and the hexamer can be described in a downward translation by one inter-strand distance and a global rotation of the second subunit, using the first one for superposition. While global characteristics of the interface, such as the buried accessible surface area, do not change very much, most of the atom-atom interactions are rearranged. It thus appears that the transmembrane domain is necessary for the proper oligomeric assembly of GLIC and that there is an intrinsic plasticity or polymorphism in possible subunit-subunit interfaces at the ECD level, the latter behaving as a monomer in solution. Possible functional implications of these novel structural data are discussed in the context of the allosteric transition of this family of proteins. In addition, we propose a novel way to quantify elastic energy stored in the interface between subunits, which indicates a tenser interface for the open form than for the closed form (rest state). The hexameric or pentameric forms of the ECD have a similar negative curvature in their subunit-subunit interface, while acetylcholine binding proteins have a smaller and positive curvature that increases from the apo to the holo form.
机译：在中性pH下以2.3 A的分辨率分离了来自Gloeobacter violaceus（GLIC）的五聚体配体门控离子通道的胞外域（ECD）的晶体结构的两种晶体形式，显示出令人惊讶的六聚四元结构轴替换预期的5倍轴。虽然每个亚基都保留了通常的β夹心免疫球蛋白样折叠，但与整个GLIC结构的微小偏差表明存在不同柔韧性的区域。五聚体和六聚体中两个相邻亚基之间的界面变化可以用一个链间距离和第二个亚基的整体旋转向下平移来描述，使用第一个亚基进行叠加。尽管界面的整体特性（例如埋入的可触及表面积）变化不大，但大多数原子-原子相互作用已重新排列。因此，似乎跨膜结构域对于正确的GLIC寡聚组装是必需的，并且在ECD级别的可能的亚基-亚基界面中存在固有的可塑性或多态性，后者在溶液中表现为单体。这些新的结构数据可能的功能含义是在该蛋白家族的变构过渡的背景下讨论的。此外，我们提出了一种新颖的方法来量化存储在子单元之间的界面中的弹性能，该方式指示了开放形式比封闭形式（静止状态）的张量界面。 ECD的六聚体或五聚体形式在其亚基-亚基界面上具有相似的负曲率，而乙酰胆碱结合蛋白具有较小的正曲率，其从apo到全环型都增加。

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